The invention relates to a process for the preparation of a polymerizable or copolymerizable composition consisting of a polymerizable unsaturated polyester or a mixture of such an ester and a monomer copolymerizable therewith and a peroxide initiator, and to the polymerization or copolymerization of like mixtures and to articles entirely or substantially composed of (co)polymerisates obtained by (co)polymerization of the compositions according to the invention.
Unsaturated polyesters may be obtained by reaction of approximately equivalent amounts of a polyvalent alcohol such as ethylene glycol, diethylene glycol, triethylene glycol, trimethylene glycol, propylene glycol, pentaerythritol and other diols or polyols with an unsaturated dibasic carboxylic acid or carboxylic anhydride such as maleic acid, maleic anhydride, fumaric acid, itaconic acid or citraconic acid. These unsaturated dibasic carboxylic acids or anhydrides are often used in combination with aromatic and/or saturated aliphatic dicarboxylic acids or the anhydrides derived therefrom, such as phthalic acid, phthalic anhydride, isophthalic acid, tetrachlorophthalic acid, malonic acid, adipic acid, sebacic acid, tartaric acid, etc.
Unsaturated polyesters containing vinyl group or vinylidene groups may be obtained by polycondensation of .alpha.,.beta.-unsaturated mono carboxylic acids such as acrylic or methacrylic acid, with mono-, di- or polyhydric alcohols. As examples of these alcohols may be mentioned: methanol, ethanol, isopropanol, cyclohexanol, phenol, ethylene glycol, propylene glycol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxycyclohexyl)propane, 2,2-bis(4-.beta.-hydroxyethyloxyphenyl)-propane, pentaerythritol and dimers thereof, trimethol propane and glycerol, and the complex diols or polyols as described in the Netherlands Patent Application No. 6 808 040, the German Patent Application DAS No. 1 645 379, the U.S. Pat. Nos. 2,895,950 and 2,628,178, the British Pat. Nos. 928,307 and 965,826 and the French Pat. No. 1 404 000.
Unsaturated polyester containing vinyl groups or vinylidene groups also may be obtained by reacting .alpha.,.beta.-unsaturated monocarboxylic acids with compounds containing epoxy groups, such as bisphenol A bis (glycidyl ether).
The unsaturated polyesters required to this end may be dissolved in monomers copolymerizable with the polyester, which contain one or more CH.sub.2 .dbd.C&lt; groups such as styrene, vinyl toluene, methylmethacrylate, ethyleneglycolmethacrylate, etc.
The solutions that are used most are those that contain 70-50% by weight of unsaturated polyester and 30-50% by weight of copolymerizable monomer. Preference is given to styrene as copolymerizable monomer.
In order to improve the stability of the unsaturated polyesters, inhibitors are incorporated in them in amounts ranging from 0.001 to 0.03% by weight. The most commonly used inhibitors are hydroquinone, quinone and paratert.butyl catechol.
The above-described unsaturated polyester or mixtures thereof with copolymerizable monomers can be (co)polymerized under the influence of hydrogen peroxide and organic hydroperoxides, ketone peroxides and diacyl peroxides, that generate free radicals.
If this (co)polymerization is to be carried out at room temperature or at a slightly elevated temperature use should be made of combinations of the afore-mentioned peroxides and accelerators, such as organic metal compounds or a tertiary amine.